Archive for November, 2011

Silly! We are not talking about your belly button! We are talking about window installations of course. Around here in the D.C. area, we do not see Innie windows very often. In fact, I don’t think I saw any before we started thinking about the issue. Typically, you will only see them on really old houses, I saw them at Mt. Vernon this week! If you ask contractors or supply houses about how to do it, the most likely response is,”why would you ever do that? We wondered about that too.

Apparently, the debate has been going on for decades among building scientists and high performance home designers. Here’s what we are able to summarize.

Outie Windows: The glazing of the window is set flush to the outside of the wall

Outie Window

Easier to install: They are installed by nailing flanges on the outer face of the wall

Simpler drainage plane: No exterior window sill to worry about

Deeper interior sill: Looks nice and you can leave a cup of coffee on the sill

Conventional looking: Everyone has it installed this way

Innie Windows: The glazing of the window is set at middle of the wall

Innie Window

Greater protection from severe weather: Innie windows are removed from the outer surface of the wall which protects them from driving rain and wind

Better supported: Unlike Outie windows which are basically secured by the screws on the window flanges, Innies are secured and supported by the wood frame

Solar shading: The recessed position of the glazing provides solar shading

Better thermal performance: The glazing being within the wall’s depth keeps the glazing within the insulated thermal envelope

We chose to do Innie Windows. This means more installation steps:

1. Starting out with over-insulation of 1″ XPS on the head and jambs. This extra layer of foam adds R-value to the window frames.

Overinsulation

2. Wrap the rough opening with Tyvak. The house wrap protects the home from damaging wind and rain.

Wrapping with Tyvak

3. Flash with Grace Vycor. We use this to build a water proof head, jamb and sill.

Flash with Grace

4. Install window. Using the expanding foam tape we previously blogged about to install the window to create an insulated, water-tight and air-tight seal around the window.

Like this:

This past week we worked on framing the interior of the home and building a slab for the garage. Intellistructures did a great job getting the interior framed quickly. I can’t wait to start finishing the interior.

Here are some pics

Landing to Terrace

1st Floor Hallway

North Star Foundations came back to build the garage slab. After they were done, Eric and I stood around, just admiring the smoothness of the surface…

Garage Slab Building

Garage Slab Building 2

Concrete Pour

Plastic Fiber for concrete

The fibers are cool. They prevent concrete from cracking and reduces the amount of rebars/wire necessary in a slab. Here’s a video of how it works (not sure what brand was used in my slab though).

The 6th North American Passive House Conference was held in Silver Spring, MD (about 20 mins from downtown DC). This was my first and I thought it was worthwhile just hearing some of the cool experiments people are doing all over the U.S. and Canada. I am sure PHIUS will upload conference materials shortly on their site but here’re some of things I found interesting from the sessions I attended.

Sam Rashkin talked about how to move PH from early adopters to mainstream consumers. Having grown the Energy Star for Homes program from nothing to nearly 30% market penetration in 15 years, I wanted to hear how he proposes to move PH to the mainstream. In short, he offers a gradual process of improving building standards in the mainstream building market until they reach the “aspiration goal” of passive house. I am not sure how I feel about that. This seems to be the Microsoft method of putting out an acceptable product then putting out an incrementally improved version every few years. I think there are enough people who know how to put out a product that is drastically better (i.e. a Passive House) that it doesn’t seem to make sense to do this gradually. However, perhaps the problem is that the vast majority of consumers do not know about Passive House and do not demand to live in one. Production builders will not make improvements on their homes unless they perceive a strong demand.

Jason Morosko explained how the ERV does/doesn’t dehumidify. I am still a little confused… What I took away was that ERVs slow down the humidification of a home on a humid day but it cannot take humidity out of a house unless the humidity level is lower outside. Also that minisplits will do enough dehumidification in most climates except in some very humid areas, where additional dehumidification strategies will be necessary. I think the D.C. area is safe… But I should probably research on this more.

Prudence Ferreria spoke about the reasoning behind Passive House’s 0.6 ACH standard. Something that has always puzzled me every time I try to explain that standard to people. I understand it as a qualitative measure of construction and that is the number that ensures safe moisture migration, but why 0.6 and not 0.65? She said that tests are being done to determine the significance of 0.6 ACH and whether that number should be more climate specific. The results of which will be presented during next year’s conference. I am a believer of building a nearly air-tight house but I am glad someone is looking into the significance of this number. Perhaps this is an opportunity that has opened up since the big split, that PHIUS can now freely question those assumptions.

My favorite lecture was one given by Thorsten Chlupp of Fairbanks, Alaska. Over the years, he built many homes in an extremely cold climate. He wanted to stop using foam due to the high embodied energy of foam production. He presented the SunRise house which is his home and personal lab (Man, I would love to have one). One of the most intriguing parts about this home is the wall assembly, which was built with CDX plywood with 22 inches of cellulose outsulation (remote wall). The cool thing is that the cellulose is wrapped in a vapor permeable membrane with no OSB or plywood holding it back on the outside. This design ensures that the wall has no vapor barrier and moisture can escape from both sides. The difficulty of implementation is off the hook!

The SunRise house uses no fossil-fuel heat sources. Instead, it uses a combination of solar thermal, thermal mass (with a massive 8 million btu storage), and a stone masonry heater. Thorsten said the last time he lit a fire was back in February. I was floored! To read more about this house check out these two articles:

Finally, Sunday was the local Passive House tour, which consisted of the Bethesda Passive House and our own Arlington Passive House. I hope people enjoyed visiting my project. I was seriously intimidated to talk about our project in front of an entire busload of experts!